The case against five United Nations peacekeepers caught on tape in an alleged sexual assault on a Haitian teenager has apparently stalled and the accused soldiers have been freed, a UN official has confirmed.

The men were sent back to Uruguay last summer to face trial after cell phone video obtained by ABC News appeared to show uniformed soldiers assaulting an 18-year-old Haitian as he is held down on a mattress in a UN compound in Port Salut, Haiti. The video shows soldiers in their UN uniforms, one of them with his pants down. The victim's mother said her son was taken inside the base by five UN soldiers who accused him of making fun of them.

The release of the accused men comes at an unsettling time for the UN in Haiti, two years after a devastating earthquake rocked the struggling island nation, and three months after the grainy video of the alleged assault triggered street protests from those who believe international peacekeepers are able to abuse Haitian citizens with impunity. Since the video surfaced, more UN peacekeepers -- this time from Brazil -- have been accused of beating Haitian civilians.

But word that the men alleged to be involved in the videotaped incident were freed poses new problems for senior United Nations officials, who told ABC News they shared the outrage over what they saw on the tape, and would stand behind the UN's pledge to end abuses by anyone in the blue-helmeted UN forces.

"The secretary general of the United Nations has a zero tolerance policy for any kind of misbehavior by soldiers," Assistant Secretary General Anthony Banbury told ABC News at the time.

At a UN Security Council meeting last summer, Uruguay's ambassador to the United Nations apologized profusely. "The government and the people of Uruguay feel extremely ashamed at the denunciation of presumed misconduct and abuse and sexual exploitation," Ambassador Jose Luis Cancela said.

Banbury noted at the time that the president of Uruguay wrote a letter to the Haitian people after the incident with a promise to deliver justice in the case.

"When there's a commitment by the head of state of a country to thoroughly investigate a crime committed in a peacekeeping mission, I'm pretty confident in that expression of commitment," he said.

Asked last week about the latest developments, UN spokeswoman Anayansi Lopez said the men were released from jail while investigators try to locate the 18-year-old Haitian victim and obtain his testimony -- something the Uruguayans said they had been unable to do. Once that occurs, she said, the men will be brought back for trial.

"The recent release of the soldiers, pending completion of the civilian trial, will not circumvent the possibility that the soldiers be re-imprisoned, should they be found guilty and sentenced accordingly," Lopez said.